A self-contained, elastic joint drive for robotics applications based on a sensorized elastomer coupling—Design and identification

• A novel, sensorized, elastomer coupling based on the principle of jaw couplings is presented.
• The elastomer coupling is integrated into a self-contained, rotatory joint drive.
• Integrated rotary position sensors measure the torsion angle of the coupling.
• A system identification of the elastomer coupling is realized and models are derived.
• Using these models with the torsion measurement the acting torque can be estimated.

While classical robotics traditionally makes use of stiff constructions in order to achieve a high precision, there is on-going research in development and control of new compliant robotic systems. These systems are suitable for direct human–machine-interaction due to their elastic behavior. The compliance is mostly achieved by control or by the integration of steel springs into the joint drives. This paper proposes a novel approach based on a sensorized elastomer coupling. Due to its damping characteristics, the interaction-safety can be improved in comparison to steel spring or purely control based approaches. The presented coupling is an integral part of a self-contained drive system which is also introduced. Simulation results of the strain/torsion and torque/torsion relationship for different geometrical variations of the elastomer coupling and experimental data of a prototype are presented. Since the sensorized coupling provides torsion measurements of the elastomer inlay, a system identification approach was employed to derive nonlinear and linear models of the coupling which can later be used in model-based joint-control.